I recently changed my oil (same type, Amsoil synthetic) and with the same type of driving, I lost 2 to 2.5mpg fuel efficiency! I've been driving in the same areas w/ the same traffic and same speeds. The oil is the same type, just changed new oil. Anyone experienced this before or know why MPG would drop? I would've assumed it would increase with fresher oil. Thanks.

J.

 

there are other factors involved that you can't change and you're simply failing to see. weather and climate changes being one of them. and to be honest, changing or not changing your oil will BARELY affect your mpg anyways.

 

it will affect it if the viscosity is substantially different.

 

which would most likely occur only if you waited a long time to change your oil. even then, it's 1mpg... 2mpg MAYBE?

 

Weather's been fairly consistent pre- and post-oil changes (it's only been about 2 weeks since I changed my oil...and I live in socal, which is fairly stable). I've filled up 3 times already since my oil change and noticed reduced mpg immediately after the oil change (I check mpg every fill up). The duration between fill ups pre- and post-oil change was about 4 days, so the weather was not that much different. My pre-oil change mpg was fairly consistent (about 0.5mpg variation). Post-oil change has also been consistent. Would this be a sign that the oil was losing viscosity at the time I changed my oil?

 

1. Check oil level, make sure that it is not way over the full mark.
2. Check cold tires pressure, make sure that they are not below 32 PSI
3. Check air box and air filter, make sure that nothing inside air box and air filter was not cloged.
4. Check sparplugs, make sure that all are in good condition.

 

Maybe a change from Winter to Summer fuel blend?

 

1. Oil level is normal
2. Tire pressure set at 32psi cold
3. Nothing in air box or intake path
4. Haven't checked spark plugs, but why would spark plug change condition after an oil change?
5. Don't think it was a change in fuel mix at the station...as I mentioned, the time between gas fill to gas fill w/ the oil change in between was about 4 days. Weather was consistent, driving habits and conditions were consistent, and this was done in early-mid April. Oh well, I guess it's just a side-effect of something.